David Bean, et al: after a little PhotoChop work, here's the artwork for your "Not 531" decal:
http://www.directcon.net/
If you take or send this .jpg file to a good printer (I use Minuteman Press; do they do business where you live?), they will make your decal. It's a little expensive to have only one made, but the unit price goes 'way down when you order more. And you will have a choice of various decal material stocks, so you should probably research it and decide beforehand what kind of decal stock you want to use. Or, you could make a reasonable facsimile yourself on a color inkjet printer by using plain old bumper sticker paper (has an adhesive backing), which is available at all larger office supply stores, such as OfficeMax and Office Depot.
Bill Crowell
Diamond Springs, California